Ok, finally I made it working again …
I create a new plugin with one admin page to understand what was going wrong. Firebug whas saying ‘wp.media is not a function’ again. And I just add an ‘wp_enqueue_media();’ in my admin page function (you know, the “$function” parameter of “add menu page”) and … Voila. wp.media was defined again, and my button work ??
So, I just add ‘wp_enqueue_media();’ at the begining of my uploading pics metabox function – yes, I’ve created a custom post type, and I’m calling some metabox on my custom post type editing page –
Now, my button is working again, and I can upload media via the WordPress Media Uploader.
The strange things is that my code was working on previous version, so maybe there is some change with ‘smith’ on that ..
Hope that will be usefull for someone